It is well known that when an infant rat or mouse is stimulated by the experimenter, in one of a variety of ways, numerous behavioral and physiological consequences can be seen in the developing and mature animal. This proposal is addressed to the hypothesis that modified maternal behavior may mediate, at least in part, the long-term consequences of experimenter-imposed early experience treatments to neonatal rodents. Maternal behavior will be observed immediately and several hours after rat pups or their mothers undergo handling or shock treatments. The effects of these treatments will be assessed further by measuring the behavioral and physiological responsiveness of the offspring when they are adults. In addition, since there is reduced adrenocortical reactivity during lactation in rats, the influence of lactation, per se, on maternal behavior under stressful conditions will be investigated by comparing the behavior of postpartum lactating and nonlactating (nipple-removed) mothers.